What was the SIZE of the White Perching-like bird you saw in Mississippi?

Black-capped Vireo: Small vireo, olive-green upperparts, black hood, white spectacles interrupted with black above the eye, white underparts with olive-yellow flanks. Wings are dark with two pale bars. Iris is red-brown to red. It has been listed as an endangered species since 1987.

Bewick's Wren: Small wren with unstreaked, gray to red-brown upperparts and plain white underparts. White eyebrows are conspicuous. Tail is long and white-edged with dark bars. Bill is long and slightly decurved. Legs and feet are gray. Eastern populations are red-brown, Northwestern birds are more brown, and Western Interior birds are gray-brown. Eastern populations have seriously declined since the 1960s.